1. Field of the Invention
The present invention relates to polyether polyols, their method of preparation, and to polyurethane compositions prepared with the polyether polyols.
2. Brief Description of the Prior Art
Polyether polyols are known in the art for the preparation of polyurethane foams. The polyether polyols are prepared by reacting a polyhydric alcohol such as sucrose with an alkylene oxide such as ethylene or propylene oxide in the presence of an alkaline catalyst such as sodium hydroxide. After reaction, the alkaline catalyst must be removed from the reaction mixture for the production of satisfactory polyurethane foams. Normally, the polyether polyol is treated with an acidic material such as phosphoric acid so as to neutralize the alkaline catalyst. This results in the precipitation of the salt which must also be removed for the production of satisfactory polyurethane foams. One of the disadvantages associated with such a process is that in removing the salt from the reaction mixture, a considerable amount of polyether polyol is lost. Also, the removed salt and polyol can pose a disposal problem.
Examples of prior art are U.S. Pat. No. 3,000,963 which discloses treating polyether polyols containing alkaline catalyst with a solid organic acid so as to form an insoluble salt which is then removed by filtration. U.S. Pat. No. 3,299,151 discloses treating polyether polyols which contain an alkaline catalyst with formic acid so as to precipitate substantially all of the catalyst and removing the precipitate by filtration or centrifugation.
The present invention differs from the prior art in that the polyether polyol containing the alkaline catalyst is treated with a hydroxy-carboxylic acid so as to form a salt which is soluble in the polyether polyol giving a clear reaction mixture. Reaction mixtures which contain insoluble salts are unsatisfactory for use with modern polyurethane processing equipment, whereas polyether polyols which contain the soluble salts of the present invention can be satisfactorily used in modern polyurethane processing equipment.
Besides the above-mentioned prior art, reference is also made to U.S. Pat. No. 4,110,268 which discloses treating polyether polyols which contain alkaline catalyst with oleic acid or mixtures of oleic acid and higher molecular weight alkyl benzene or alkyl toluene sulfonic acids such as dodecylbenzene sulfonic acid. The resultant neutralized salt is soluble in the polyether polyol composition. However, it appears that these particular salts have catalytic activity for a subsequent polyurethane foaming reaction. This can be a disadvantage in that it reduces the control over the polyurethane foaming reaction. Normally, polyurethane foaming reactions are catalyzed with amines in a well-known and well-defined manner. Foaming times are easily adjusted by the type and amount of the well-known amine catalyst. Neutralizing with the acids disclosed in U.S. Pat. No. 4,110,268 can present problems of controlling the catalysis of the polyurethane foaming reaction. In the present invention, on the other hand, salts formed by the hydroxy-carboxylic acids have no appreciable catalytic activity for the polyurethane foaming reaction, and, therefore, the well-known amine catalyst can be used.